(1) Field of the Invention
The present invention relates to an orientable longitudinal structure and to its method of manufacture, said structure comprising substantially longitudinal actuators made of shaped memory alloy (SMA), n-doped and p-doped Peltier elements and electrical operating means.
Such a structure is intended in particular for endoscopes, whether these be used in the medical field or in industry.
(2) Prior Art
Endoscopes are optical systems allowing inaccessible areas to be explored visually. They comprise, in particular, a flexible body of variable length intended to be introduced into the area that is to be inspected and on the end of which a viewing system is mounted. The end of the head of the endoscope is articulated so that the viewing system can be pointed in several directions, thus allowing the region that is to be inspected to be seen.
The prior art already discloses numerous solutions for orientating the heads of endoscopes.
Apart from the conventional mechanical control systems that use steel cables connecting the head of the endoscope to the operator's control member, the prior art also discloses solutions based in particular on the use of shaped memory alloys.
U.S. Pat. No. 5,624,380 proposes a manipulator with several degrees of freedom exhibiting a plurality of flexible parts that can be flexed selectively.
Said manipulator consists of a flexible tube comprising:                a plurality of flexible parts arranged in rows,        a plurality of SMA actuators,        power transmission means (such as conducting wires) for transmitting power to the actuators, running along the flexible tube,        power supplying elements arranged in series between said power transmission means and said actuators so as to control the energy supplied to the actuators by said power transmission means.        
According to one embodiment of the invention, the manipulator comprises a plurality of substantially cylindrical flexible parts arranged in an axial direction. A pair of thermally deformable elements, each consisting of a leaf of SMA, is arranged between the front flexible parts and the adjacent rear flexible parts in order to curve said flexible parts.
Japanese patent application JP200135288 also discloses a cylindrical mobile element for an endoscope or catheter, it being possible for said cylindrical element to be flexed or turned in a required direction with a rapid response rate.
To do this, said cylindrical element comprises a plurality of elements made of SMA and p-doped and n-doped Peltier elements. These elements are arranged alternately and held between plastic rings exhibiting a central cavity.
The p-doped and n-doped Peltier elements are connected in series by electrodes such that the heat-generating parts and the heat-absorbing parts are in the same position. The elements are curved in a required direction by the selective application of current to the Peltier elements.
The systems described hereinabove do, however, present numerous disadvantages.
As far as the conventional mechanical systems are concerned, these have the disadvantage of generating significant friction between the control cables and the endoscope sheath, thereby limiting the useful exploration length.
Furthermore, local control of each articulation is impossible, thereby generating a risk of contact with certain areas of the environment explored, which risks are particularly damaging in the case of medical functional explorations.
As far as the systems developed in the Japanese patent application or the American patent which are cited hereinabove are concerned, these also present certain disadvantages.
In particular, the SMA actuators used are generally in the form of wires. Now, such wires exhibit relatively restricted elongation as a function of temperature. In order to obtain actuators that produce sufficient movement it is then necessary to have relatively long wires.
Furthermore, such systems display the disadvantage of leading to endoscopes that are relatively bulky because of the nature of the actuators and their positionings in the endoscope. Such actuators effectively generally limit the internal space of the endoscope or increase the outside diameter thereof.